Method of measuring the strength of fibers



r 1,643 333' sti'pt' 19277 .E. E. CHANDLER METHOD OF MEASURING THE STRENGTH OF FIBERS Filed May '7. 1925 i' 2- I i wm w material compassing it.

Patented Sept. 27,1927.

-, UNITED STATES I 1,643,333- PATENT, oFFrca.

EL'BERT n. c'nannnnn, or Los anennns, CALIFORNIA.-

nnrnonor MEASURING THE srnnne'rn or rrnnns.

Application flied May 7, 1925. SerialNo. 28,697. I

My invention relates particularly to cotton fiber, although it may be applied to 'haig's, filaments and other fibers, such as are used mainly in textiles: It consists in the prep-' aration of a bundle of such fibers, the measurement of the superficial cross sectional area of the bundle, the reduction of this superficial area to the area of the material tested, with eliminationof the interstices or voids, the preparation of the bundle for unit breakage, the final breakage of the bundle and the calculation of the strength of the Present methods of testing small fibers consist of breaking single fibers to determine their strength. In a test recently made the strength of a series of one hundred fibers of cotton taken at, random was found to vary from two grams to 14.5 grams so that little reliability can be placed on this method without a large number of tedious operations. Other methods such as twisting together a certain weight of fibers and breaking them and also breaking a number of; parallel fibers whose ends had been pasted to a card board and the cardboard slit into two portions so that the strain'came entire-- ly on the of the cellulose, but merely the average strength of the fiber. They are also subject toa number of other limitations and have I found no practical use.

. wrapped. To do so it is clamped in the.

The bundle of fibers is prepared in a manner similar to that used by the cotton stapler, when he estimate the length of the fiber. I prefer however to further even'- up the bundle or pull by combing'it at successive stages through a stationary comb.

- This makes thefiber more parallel and removes motes and tangles, which it is impossible to entirely remove by hand. I

The bundle is then wrap d with thread by means of the machine i lustrated inthe accompanying drawing in which, Figure 1 represents a top view of the wrapping device, Figure 2 a front elevation and Figure 3 a bundle of cotton to whose ends a thread has been tied and which is ready to be jaws a and a. The bundle b is then stretched by the weight 0, suspended by the string d running over the pulley e from the swivel f, attached to the shaft 9, integral with the jaw a. ,The' jaw ai's made to rofibers, have been tried. These methods however do not give the strengthtate with the jaw a by h, k, h" and k and the jack shaft i, when the shaft gv is rotated by the cranky.

The thread is is thus wra ped on the bundle, while being stretche by the second weight Z. Weights'l and a of one and two pounds, two and five and four and ten pounds respectively have been tried and a number 20. thread has been found sufficient" to suspend the'smaller or wrapping weight. The greater the weight on the wrapping thread the greater the degree of condense-- tion of the fibers or the elimination of the interstices between them. Slightly greater condensation results also when the bundles have been wet with alcohol rinsed with the constant by which to multiply the result in order to eliminate the voids by K, then Ar D p wm, -x- 1- -2 The cellulose strength S may also-be found more directly if the length of the bundle is KB 4KIIB.

means of the gears I known. However the fibers in the bundle are of varying lengths and this length of'the bundle can not be determined by direct measurement. A method has been devised to determine this average cellulose length and, if the weight of the bundle be represented by W, the density of cellulose or other material by De,the volume by V, its area by A and the averagelength by L, then;'

The value of. K is merely thei -ratio of. the

areas A, and A, obtained by. the two'niethods, or 4 2 v A 4 CDeLf I, W 4nW f To obtain the-value of K, L m'a be made short enoughtq include allthe fi rs. This i was done'by lacing the wra ed bundle under a straig t edge three eig ths of {an inch wide and pressing upon it with a sharp knife.

The density of cellulose in-the metric system is usually -given as 1.5. The three eighths inch bundle was dried, unwrapped and wei hed in grams. Converting all terms.

to the llnglish system of units and the values of K were found at the various tensions and conditions investigated. At two and five pound tensions, wettin the cotton and allowing it to dry to stan ard conditions this constant K was found to be 1.7 6, whereas when the cotton was wrapped wet the K became 1.64. Whenwrapped at four and ten pound tensions K, when cotton had never been wet, was 1.62, whenwet and allowed to dry 1.56 and when wra ped wet 1.61. When the bundle had never en Wet and the value of K was 1.62 the formula for.

middle. When the three windings met they reversed their direction and moved to the ends. This left a place in the middle of the bundle which was so pkported by the fiber alone when stressedint ebreak'er jaws. The

position of the indicator on the scale n was noted when the wrappings were about three sights of an inch apart and then a ain after ten revolutions of the crank. This allowed. an easy calculation of the denominater of.

the last equation. The break'was made on the ordinary yarn breaker, although s ecial' laws had to be constructed to hol the undle- 10,000 fiberswere found to have 8.

circumference of about .16 inches and to break at about 100 pounds. Bundles from half this number to three times this number were found to give good agreement for the strength of cellulose by this formula.- No

account need be'taken for the thickness of u the wrapping thread as the circumference occurs in the numerator in determining the value of K and in the denominator in determining the value of S. The cellulose of difi'erent cottons was found to vary considerably, running. from 100,000 pounds to the squareinch to about half that amount. The results by this method were compared with those by the single fiber method and found to be in good agreement, without-the seven hundred per cent difierence exhibited by single fibers. The probable error by this method is less than 2 per cent.

l/Vhile wrapping a round body 'is a. well known method of obtaining its area, yet it is done here not only for this purpose but also to prepare the bundle to give a sharp snappy break. This break always occurs where the wrappings have met and resistance can only be-due to the fibers. Other methods of Wrapping have been tried, such "as for instance wrapping only in one direction.

This gives a slightly greater strength to the. bundle, but the question arises whether some of the apparent strength is not due to the and runs transverse to the fiber.

- Having thus described my'invention what .I claim and desire to secure by Letters Patout, is

thread, even though the thread is not broken I A method of measuring the strength of fibers; consisting in laying them parallel with each othen, wrapping them with 'a thread to obtain the superficial area of the bundle and to prepare it for aneven break and breaking the bundle to" obtain its strength.

IELBERTE. CHANDLER. 

